1. Field
The present invention relates to a linear drive with a stator, a runner, and two rotative drive units provided for driving the runner.
2. Description of Related Art
A linear drive of the kind previously mentioned is known for example from DE 199 33 234 A1. The linear drive disclosed therein comprises a rotatably mounted spindle which serves to drive a carriage movably mounted in the axial direction of the spindle. The spindle is driven by two electric motors which are disposed at opposite ends of the spindle. The two electric motors always have the same direction of rotation. The torque acting upon the spindle is therefore generated to equal amounts by the two electric motors. By using two electric motors instead of a single electric motor, compact construction of the linear drive is enabled, the motor size is reduced, and the vibration noise is lessened.
A linear drive is known from DE 100 46 137 A1 in which the two drive units are alternately coupled to the runner of the linear drive in order to thereby achieve a continuous motion of the runner. The two drives can be embodied, for example, as bistable lifting magnets, lifting magnets with a passive return spring, piezo transducers, pneumatic cylinders or SMA actuators. The force coupling between the drives and the runner can be effected by a magnetic coupling mechanism, by electrostatic forces of attraction, or any appropriately designed mechanical configurations. Friction forces, magnetic and electrostatic forces, media changing their viscosity or elasticity, and changing chemical binding forces are generally spoken of in connection with the force coupling.
Many applications of linear motors today require highly dynamic drives, which are also subject to increased requirements in terms of compact design.